Fill in the missing key words Key word

Fill in the missing key words Key word Definition The number of individuals in a population. A variable that limits the rate of a chemical reaction (i. e respiration) and therefore limits growth. Permanent changes to the structure, and hence threedimensional shape, of a protein due to factors such as changes in temperature or p. H. More or less self-contained functional unit in ecology made up of all interacting biotic and abiotic factors in a specific area. Evaporation of water from a plant.

Key words & definitions Key word Definition Population size The number of individuals in a population. Limiting factors A variable that limits the rate of a chemical reaction (i. e respiration) and therefore limits growth. Denaturation Permanent changes to the structure, and hence threedimensional shape, of a protein due to factors such as changes in temperature or p. H. Ecosystems More or less self-contained functional unit in ecology made up of all interacting biotic and abiotic factors in a specific area. Transpiration Evaporation of water from a plant.

Population Size • Population - number of organisms of the same species that live in the same place at the same time that can interbreed • Population growth is eventually slowed by a limiting factor. • Species can only live within a certain range of abiotic factors and this range differs from species to species.

Studying population size using bacteria • Image a small number of bacteria have been placed into a sealed container • It contains nutrient and oxygen • What will happen to the population size over time?

Bacterial Growth Curve Time /hours 0 Number of Bacteria 2 1 4 2 8 3 16 4 32 5 64 6 128 7 128 8 78 • Draw a graph of the data • Describe any changes in population growth • Explain any changes in population growth 15 minutes

Check your graph! • • • Correct choice of graph (line) Axes the right way around (time on x axis) Suitable scale (to allow accurate plotting) Labels with units Accurate plotting Appropriate line (dot to dot is fine)

Log scales A logarithmic scale is a nonlinear scale used when there is a large range of quantities. Common uses include the earthquake strength, sound loudness, light intensity, and p. H of solutions. It is based on orders of magnitude, rather than a standard linear scale, so each mark on the scale is the previous mark multiplied by a value.

Bacterial Growth • The bacteria population will grow until a factor limits growth • These are called limiting factors…

Limiting Factors • • • Limiting factors in growth culture? Amount of nutrients. Amount of oxygen Levels of excretory factors. In nature, a variety of factors may be limiting.

Limiting Factors in the wild • More complex • Biotic and abiotic factors influence population • All of the above will put an upper limit on numbers – carrying capacity.

Carrying Capacity • Unlike the bacteria in the flask, food very unlikely to totally run out. • Environmental factors affect numbers • Difficult to control all factors when we study population sizes.

Population Growth Curve

To Do: 20 minutes • Explain how each abiotic factor might affect the population size of organisms • Can you add any other abiotic factors? • Add biotic factors to the diagram • Page 470 might help

Temperature Temp affects enzyme activity Humidity affects transpiration from plants and water loss from animals Biotic factors: Competition Predation Parasites and pathogens Water availability Very dry environments – few species that are adapted to and low population size Cold blooded orgs – low temps slow metabolic rate, high temps denature enzymes Warm blooded orgs – more consistent body temp but further away from optimum temp means less energy available for reproduction p. H Factors Affecting Population Size Affects enzyme activity Light Affects rate of photosynthesis More photosynthesis means more growth and reproduction in plants This affects animal population as plants are a source of food

Population Size Which abiotic factor is most likely going to limit population size of: • Ground plants on forest floor • Hares in a sandy desert • Bacteria on the summit of a high mountain

Population Size Which abiotic factor is most likely going to limit population size of: • Ground plants on forest floor – light intensity • Hares in a sandy desert – water availability • Bacteria on the summit of a high mountain temperature

Population Growth Homework • Choose a species and briefly outline it’s habitat • List the limiting factors of the carrying capacity of the habitat